Effect of introducing thymine spacers into an adenine strand: Electronic decoupling?
Electronic coupling between DNA bases governs the deexcitation pathways after light absorption as well as the ability of the DNA strand to conduct charge. UV excitation of single strands of adenine bases involves two adjacent bases while the spatial extent of the excited state wavefunction following VUV excitation is over eight bases. In this work, we have recorded synchrotron radiation circular dichroism spectra for a series of DNA strands on the form AnTmAn, n = 1–5 and m = 1–3, in aqueous solution to study the effect of introducing thymine spacers on the electronic coupling between the adenines. We find that a single thymine spacer is enough to eliminate the strong coupling between the adenine bases for all excitation wavelengths between 175 nm and 330 nm.
► Electronic coupling between two adenines in DNA strands is broken by a thymine spacer. ► Synchrotron radiation CD spectra of AnTmAn (n = 1?5 and m = 1?3) are reported. ► CD spectra of dAnTmAn strands can be calculated from smaller-strand reference spectra.
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 220, Issue 1, 30 April 2011, Pages 1–3